1. Field of the Invention
The present invention relates to improved air conditioning systems which utilize at least one refrigeration cycle circuit to carry out room cooling and room heating operation.
2. Discussion of Background
Such type of air conditioning systems have been constructed as shown in "HEAT PUMP--Practical Design and Application--" (page 122 FIG. 4. 12). An example of the conventional air conditioning systems will be described briefly with reference to FIG. 9. In FIG. 9, reference numeral 1 designates a compressor. Reference numeral 2 designates a four port reversing valve. Reference numeral 3 designates an outdoor heat exchanger. Reference numerals 4 and 5 designate a first throttle device and a second throttle device, respectively, which function as expansion devices on room heating and on room cooling, respectively. Reference numeral 6 designates an indoor heat exchanger. Reference numeral 7 designates an accumulator. These members are connected in series by refrigerant pipes to form a refrigeration cycle circuit. Reference numerals 8 and 9 designate an indoor fan and an outdoor fan, respectively, which feed air to the indoor heat exchanger 6 and the outdoor heat exchanger 3, respectively. Reference numerals 4a and 4b designate a first decompression device (capillary tube) and a first check valve, respectively, the first check valve being arranged in a circuit for bypassing the first decompression device. The first decompression device and the first check valve constitute the first throttle device 4. Reference numerals 5a and 5b designate a second decompression device (capillary tube) and a second check valve, respectively, the second check valve is arranged in a circuit for bypassing the second decompression device. The second decompression device and the second check valve constitute the second throttle device 5.
The operation of the air conditioning system as constructed above will be described.
On room cooling (the flow of a refrigerant is indicated by arrows of thick solid lines in FIG. 9), the refrigerant that has been discharged from the compressor 1 and has become a gas having high temperature under high pressure passes through the four port reversing valve 2. In the outdoor heat exchanger 3, the gaseous refrigerant carries out heat exchange with the outside air which is fed by the outdoor fan 9, thereby being condensed and liquefied. The refrigerant thus liquefied passes through the first check valve 4b in the bypass circuit of the first throttle device 4, and is taken into the second decompression device 5a forming a part of the second throttle device 5, thereby being decompressed and becoming a liquid refrigerant having low temperature under low pressure. After that, the liquid refrigerant enters the indoor heat exchanger 6, carries out heat exchange with the indoor air which is fed by the indoor fan 8. As a result, the liquid refrigerant cools the indoor air to be evaporated. The refrigerant thus evaporated returns to the compressor 1 through the four port reversing valve 2 and the accumulator 7. The refrigeration cycle on cooling is formed in this manner. The refrigerant is circulated in the refrigeration cycle circuit, repeating the foregoing liquefaction and evaporation in that order.
On heating (the flow of the refrigerant is indicated by arrows of thin solid lines in FIG. 9), the refrigerant which has been discharged from the compressor 1 and has become a gas having high temperature under high pressure passes through the four port reversing valve 2 which has been switched to heating mode. The gaseous refrigerant enters the indoor heat exchanger 6, and carries out heat exchange with the indoor air which is fed by the indoor fan 8. As a result, the refrigerant heats the indoor air to be condensed and liquefied. After that, the refrigerant thus liquefied passes through the second check valve 5b which is arranged in the circuit for bypassing the second throttle device 5. The refrigerant is directed to the first decompression device 4a forming a part of the first throttle device 4. In the first decompression device, the refrigerant is depressurized to become a liquid refrigerant having low temperature under low pressure. After that, the refrigerant thus liquefied enters the outdoor heat exchanger 3, and carries out heat exchange with the outdoor air which is fed by the outdoor fan 9. As a result, the refrigerant absorbs heat from the outdoor air to cool it and to be evaporated. The refrigerant thus evaporated returns to the compressor 1 through the four port reversing valve 2 and the accumulator 7. The refrigeration cycle on heating is formed in this manner.
When such heating operation is continued, frost can be produced on the outdoor heat exchanger 3 in e.g. the case wherein the temperature of the outdoor air is low. When the frost has deposited on the outdoor heat exchanger in large amounts, heat exchange efficiency deteriorates. As a result, the heat absorption amount from the outdoor air decreases to significantly lower the heating capacity of the system. For this reason, defrosting is required in such case. The defrosting operation has been made as described in the article "HEAT PUMP--Practical Design and Application--" (page 121).
Referring to FIG. 9, on the defrosting operation (the flow of the refrigerant is indicated by arrows by dotted lines in FIG. 9), the refrigerant which has been discharged from the compressor 1 and has become a gas having high temperature under high pressure passes through the four port reversing valve 2 which has been switched from heating mode to cooling mode. Then, the refrigerant enters the outdoor heat exchanger 3 with the outdoor fan 9 stopped. The frost which has deposited on the outer surface of the outdoor heat exchanger 3 is melted by the gaseous refrigerant having high temperature. As a result, the refrigerant is condensed and liquefied. The refrigerant thus liquefied passes through the first check valve 4b forming a part of the first throttle device 4. The refrigerant is depressurized by the second decompression device 5a forming a part of the second throttle device 5, thereby being a gas having low temperature under low pressure. Then, the refrigerant thus liquefied enters the indoor heat exchanger 6. The refrigerant returns to the compressor 1 through the four port reversing valve 2 and the accumulator 7. The refrigeration cycle on the defrosting operation is formed in this way.
FIG. 10 is a schematic diagram showing the refrigerant circuit of another conventional air conditioning system wherein a first refrigeration cycle circuit and a second refrigeration cycle circuit are independently provided, and the indoor heat exchangers arranged in the respective refrigeration cycle circuits are fed air by a common fan. In FIG. 10, reference numeral 1a0 designates a compressor. Reference numeral 2a designates a four port reversing valve which can switch operation modes in the first refrigeration cycle circuit. Reference numeral 3a designates an outdoor heat exchanger. Reference numerals 4a and 5a designate a first throttle device and a second throttle device, respectively, which function as expansion devices on heating and on cooling, respectively. Reference numeral 6a designates an indoor heat exchanger. Reference numeral 7a designates an accumulator. These members are connected in series by refrigerant pipes to form the first refrigeration cycle circuit. Reference numeral 9a designates an outdoor fan which feeds air to the outdoor heat exchanger 3a. Reference numerals 4aa and 4ab designate a first decompression device (e.g. a capillary tube) and a first check valve, respectively, the first check valve being arranged in a circuit for bypassing the first decompression device. The first decompression device and the first check valve constitute the first throttle device 4a. Reference numerals 5aa and 5ab designate a second decompression device (e.g. a capillary tube) and a second check valve, respectively, the second check valve being arranged in a circuit for bypassing the second decompression device. The second decompression device and the second check valve constitute the second throttle device 5a.
Reference numeral 1b0 designates a compressor. Reference numeral 2b designates a four port reversing valve which can switch operating modes in the second refrigeration cycle circuit. Reference numeral 3b designates an outdoor heat exchanger. Reference numerals 4b and 5b designate a first throttle device and a second throttle device, respectively, which function as expansion devices on heating and on cooling, respectively. Reference numeral 6b designates an indoor heat exchanger. Reference numeral 7b designates an accumulator. These members are connected in series to form the second refrigeration cycle circuit 11.
Reference numeral 9b designates an outdoor fan which feeds air to the outdoor heat exchanger 3b. Reference numerals 4ba and 4bb designate a first decompression device (e.g. a capillary tube) and a first check valve, respectively, the first check valve being arranged in a circuit for bypassing the first decompression device. The first decompression device and the first check valve constitute the first throttle device 4b. Reference numerals 5ba and 5bb designate a second decompression device (e.g. a capillary tube) and a second check valve, respectively, the second check valve being arranged in a circuit for bypassing the second decompression device. The second decompression device and the second check valve constitute the second throttle device 5b.
Reference numeral 8 designates a common fan which feeds air to the indoor heat exchanger 6a in the first refrigeration cycle circuit 10 and to the indoor heat exchanger 6b in the second refrigeration cycle circuit 11.
The operation of the air conditioning system having such structure will be described.
Firstly, the operation of the first refrigeration cycle circuit 10 will be explained. In the first refrigeration cycle circuit 10, on cooling (the flow of the refrigerant is indicated by arrows of thick solid line in FIG. 10), the refrigerant which has been discharged from the compressor 1a0 and has become a gas having high temperature under high pressure passes through the four port reversing valve 2a. In the outdoor heat exchanger 3a, the gaseous refrigerant carries out heat exchange with the outdoor air which is fed by the outdoor fan 9a, thereby being condensed and liquefied. The refrigerant thus liquefied passes through the check valve 4ab in the bypass circuit at the first throttle device 4a, and is directed to the second decompression device 5aa constituting the second throttle device 5a. The refrigerant is depressurized there to become a liquid having low temperature under low pressure. After that, the refrigerant thus liquefied enters the indoor exchanger 6a, and carries out heat exchange with the indoor air which is fed by the indoor fan 8. As a result, the liquid refrigerant cools the indoor air to be evaporated. The refrigerant thus evaporated returns to the compressor 1a0 through the four port reversing valve 2a and the accumulator 7a. The refrigeration cycle on cooling is formed in this manner. The refrigerant circulates in the refrigeration cycle circuit, repeating the foregoing liquefaction and evaporation in that order.
Secondly, on heating (the flow of the refrigerant is indicated by arrows of thin solid line in FIG. 10), the refrigerant which has been discharged from the compressor 1a0 and has become a gas having high temperature under high pressure passes through the four port reversing valve 2a which has been switched to heating mode. The gaseous refrigerant enters the indoor heat exchanger 6a, and carries out heat exchange with the indoor air which is fed by the indoor fan 8. As a result, the gaseous refrigerant heats the indoor air to be condensed and liquefied. The refrigerant thus liquefied passes through the second check valve 5ab in the second throttle device 5a, and is directed to the first decompression device 4aa constituting the first throttle device 4a. The liquid refrigerant is depressurized there to become a liquid having low temperature under low pressure. After that, the liquid refrigerant enters the outdoor heat exchanger 3a, and carries out heat exchange with the outdoor air which is fed by the outdoor fan 9a. The liquid refrigerant absorbs heat from the outdoor air to cool the outdoor air and to be evaporated. The refrigerant thus evaporated returns to the compressor 1a0 through the four port reversing valve 2a and the accumulator 7a. The refrigeration cycle on heating is formed in this way.
When such heating operation is continued, frost can deposit on the outdoor heat exchanger 3a in e.g. the case wherein the temperature of the outdoor air is low. When frost has deposited on the outdoor heat exchanger 3a in large amounts, heat exchange efficiency deteriorates. As a result, the heat absorption amount from the outdoor air decreases to significantly lower the heating capability of the system. For this reason, defrosting is required in such case.
On such defrosting operation (the flow of the refrigerant is indicated by arrows of dotted line in FIG. 10), the refrigerant which has been discharged from the compressor 1a0 and has become a gas having high temperature under high pressure passes through the four port reversing valve 2a which has been switched from the heating mode to cooling mode. Then, the gaseous refrigerant enters the outdoor heat exchanger 3a with the outdoor fan 9a stopped. The frost which has deposited on the outer surface of the outdoor heat exchanger 3a is melted by the gaseous refrigerant having high temperature. It causes the refrigerant to be condensed and liquefied. The refrigerant thus liquefied passes through the first check valve 4ab in the first throttle device 4a, and is depressurized by the second decompression device 5aa constituting the second throttle device 5a, thereby becoming a liquid having low temperature under low pressure. Then, the liquid refrigerant enters the indoor heat exchanger 6a, and returns to the compressor 1a0 through the four port reversing valve 2a and the accumulator 7a. The refrigeration cycle on the defrosting operation is carried out in this manner. Explanation on the cooling operation, the heating operating and the defrosting operation of the second refrigeration cycle circuit 11 will be omitted because those of the second refrigeration cycle circuit 11 are made like those of the first refrigeration cycle circuit 10.
In the conventional system as shown in FIG. 9, the introduction of the liquid refrigerant having low temperature under low pressure to the indoor heat exchanger 6 on defrosting under the heating operation creates some problems. Specifically, the indoor fan 8 which is arranged to face toward the indoor heat exchanger 6 carries out a breeze operation wherein a gentle wind is fed, or is stopped on the defrosting operation. When the breeze operation is carried out, the liquid refrigerant having low temperature under low pressure carries out heat exchange with the indoor air to cool it, and to be evaporated. The refrigerant thus evaporated returns to the compressor 1 through the four port reversing valve 2 and the accumulator 7. In this case, cool air is blown off indoors, thereby providing a disadvantage in that room heating effect significantly deteriorates.
When the indoor fan 8 is stopped, the liquid refrigerant having low temperature under low pressure can not absorb heats from the indoor air. The refrigerant enters the accumulator 7 and returns to the compressor 1 in the form of a liquid. As a result, the compressor 1 has to compress the liquid, causing trouble in the compressor.
In addition, in the conventional system shown in FIG. 9, the pressure at the high pressure side is low, particularly on defrosting, and the pressure at the lower pressure side therefore lowers, providing disadvantages in that the compressor 1 is prevented from achieving the best performance, and that the defrosting time is long. Further, on heating, the four port reversing valve 2 is switched to the cooling mode to carry out the defrosting operation, creating the problem wherein heat loss is caused at the time of switching.
On the other hand, in the conventional air conditioning system as shown in FIG. 10, the indoor heat exchangers 6a and 6b in the first and second refrigeration cycle circuits 10 and 11 which are independent of each other are fed air by the common fan 8. This arrangement can not stop the fan 8 because when either (e.g. the first refrigeration cycle circuit 10) of the first and second refrigeration cycle circuits 10 and 11 carries out the defrosting operation on heating to introduce the liquid refrigerant having low temperature under low pressure into the indoor heat exchanger 6a in the first refrigeration cycle circuit 10, the other refrigeration cycle circuit or the second refrigeration cycle circuit 11 is under the heating operation. As a result, in the indoor heat exchanger 6a of the first refrigeration cycle circuit 10, the liquid refrigerant having low temperature under low pressure carries out heat exchange with the indoor air to blow out the cooled air into the room with the indoor heat exchanger in it, thereby significantly deteriorating the room heating effect. In addition, the pressure at the high pressure side is low on the defrosting operation, and the pressure at the low pressure side therefore lowers, thereby preventing the compressor laO from achieving the best performance and causing the defrosting time to be lengthened. Further, on heating, the four port reversing valve 2a is switched to the cooling mode to carry out the defrosting operation, thereby providing a disadvantage in that heat loss is caused at the time of switching.